(481d) Municipal Water Bacteria Content Monitoring through Acoustic Wave Sensors

The health of the world's population is dependant on the quality of municipal water supplies, which is dependent on current technology to monitor the levels of bacterial content. Current methods used to monitor biological contamination include the presence/absence and the standard plate count method. This technology also focuses on the presence of E. coli and total coliform bacteria usually related to feacal contamination of a water source and it has remained essentially unchanged for 100 years. We present a new approach to water quality assessment that monitors the growth of specific pathogenic bacteria directly on an acoustic wave device namely the quartz crystal microbalance (QCM) eliminating expensive analytical tools and time consuming operations. This technique includes the use of selective growth media, coated on the surface of the QCM, to produce the growth of target bacteria and reduce the effects of non-desired bacteria growth. Greater sensitivity coupled to easy integration with common electronics makes for a versatile sensor that can be combined with other sensors to provide unparalleled performance at low costs. The utilization and optimization of QCM response to the bacterial growth allows time sensitive results to be obtained quickly, resulting in safer, more productive environments. Using a 5 MHz QCM, results show that bacteria concentrations 2 magnitudes higher than the generally accepted heterotrophic bacteria concentration, of 200-500 cells per mL, can be determined within 90 minutes where as the standard procedure takes a minimum of 24 hours. At concentrations closer to real scenarios, the time for determination is within 3 hours. Furthermore, for future implementation the use of several devices in parallel devices can increase the precision of enumeration using this technique. Also, E. coli was used for the initial testing of the concepts and further tests have shown that more information can be attained through testing for multiple types of bacteria and determining the growth characteristics of each within the sensor.